a view from modern soft X-ray spectroscopies

Soft X-ray spectroscopies are powerful tools for probing the local electronic and molecular orbital structures of materials in different phases and various environments. While modern spectroscopic tools using soft X-ray synchrotron photons perspicuously reveal the molecular orbital (MO) structure in detail, structures remain widely unknown in the liquid phase since many of these techniques could only be applied to solutions very recently. Furthermore, the interactions and dynamics of molecules in the liquid phase are especially complicated compared to those in gas and solid phases and thereby impede the understanding of functional materials in solution. This review presents recent developments using soft X-ray radiation for probing the electronic structure of ions and molecules in solution. The presented X-ray absorption, emission, and photo-electron spectroscopy studies exhibit the powerful contributions of soft X-ray liquid spectroscopies in the last few years

recent techniques and applications using soft X-ray spectroscopy

The aim of a more precise knowledge about molecular structures and the nature of chemical bonds is the driving force behind the development of numerous experimental methods and theories. Recent soft X-ray based techniques provide novel opportunities for tackling the structure and the dynamics of chemical and biochemical systems in solution. In our research group we are developing experimental methods for mapping the electronic structure and dynamics of molecular systems in solution during bond-building and breaking using soft X-ray absorption and emission spectroscopy. The combination of such recent developments with conventional spectroscopy as well as theoretical modeling allows us to address open questions about hydrogen bonds, thermodynamics and active centers of biological systems. Based on the core-hole clock and pump–probe spectroscopy dynamics on the time scale from sub-femtoseconds up to picoseconds can be revealed

an iron L-edge X-ray absorption study of the active centre

Iron L-edge X-ray absorption spectra of the active centre of myoglobin in the met-form, in the reduced form and upon ligation to O2, CO, NO and CN are presented. The strength of ligation with the iron centre is finger-printed through the variation of the L3 : L2 intensity ratio. Charge Transfer Multiplet calculations are performed and give qualitative information about oxidation states as well as charge transfer

One-Pot Synthesis of nickel-modified carbon nitride layers toward efficient photoelectrochemical cells

[EN] A new method to significantly enhance the photoelectrochemical properties of phenyl-modified carbon nitride layers via the insertion of nickel ions into carbon nitride layers is reported. The nickel ions: are embedded within the carbon nitride layers by manipulating the interaction of Ni ions and molten organic molecules at elevated temperature prior to their condensation. A detailed analysis of the chemical and photophysical properties suggests that the nickel ions dissolve in the molten molecules, leading to the homogeneous distribution of nickel atoms within the carbon nitride layers. We found that the nickel atoms can alter the growth mechanism of carbon nitride layers, resulting in extended light absorption, charge transfer properties, and the total photoelectrochemical performance. For the most photoactive electrode, the Ni ions have an oxidation state of 2.8, as confirmed by soft X-ray absorption spectroscopy. Furthermore, important parameters such as absorption coefficient, exciton lifetime, and diffusion length were studied in depth, providing substantial progress in our understanding of the photoelectrochemical properties of carbon nitride films. This work opens new opportunities for the growth of carbon nitride layers and similar materials on different surfaces and provides important progress in our understanding of the photophysical and photoelectrochemical properties of carbon nitride layers toward their implantation in photoelectronic and other devices.We thank the use Katz Institute for Nanoscale Science & Technology Ben Gurion University for HR-TEM measurements. M.S. thanks Dr. Laurent Chabanne for fruitful discussion. K.M.L. is grateful for the support by the Helmholtz Association (VH-NG-1140).Zhang, W.; Albero-Sancho, J.; Xi, L.; Lange, KM.; García Gómez, H.; Wang, X.; Shalom, M. (2017). One-Pot Synthesis of nickel-modified carbon nitride layers toward efficient photoelectrochemical cells. ACS Applied Materials & Interfaces. 9(38):32667-32677. https://doi.org/10.1021/acsami.7b08022S326673267793

Hydrophilic nanoparticles stabilising mesophase curvature at low concentration but disrupting mesophase order at higher concentrations

Silica nanoparticles form aggregates at mesophase domain boundaries, which may suppress or promote curvatures depending on the nanoparticle concentration.</p

oxygen K-edge X-ray absorption and emission spectroscopy on micro-jets

Oxygen K-edge X-ray absorption, emission, and resonant inelastic X-ray scattering spectra were measured to site selectively gain insights into the electronic structure of aqueous zinc acetate solution. The character of the acetate ion and the influence of zinc and water on its local electronic structure are discussed

Ion pairing versus water structure modifications

The effect of monovalent cations (Li+, K+, NH4 +, Na +) on the water structure in aqueous chloride and acetate solutions was characterized by oxygen K-edge X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy, and resonant inelastic X-ray scattering (RIXS) of a liquid microjet. We show ion- and counterion dependent effects on the emission spectra of the oxygen K-edge, which we attribute to modifications of the hydrogen bond network of water. For acetates, ion pairing with carboxylates was also probed selectively by XAS and RIXS. We correlate our experimental results to speciation data and to the salting-out properties of the cations

Polymersomes at the solid-liquid interface:Dynamic morphological transformation and lubrication

Polymersomes are hollow spheres self-assembled from amphiphilic block copolymers of certain molecular architecture. Whilst they have been widely studied for biomedical applications, relatively few studies have reported their interfacial properties. In particular, lubrication by polymersomes has not been previously reported. Here, interfacial properties of polymersomes self-assembled from poly(butadiene)-poly(ethylene oxide) (PBD-PEO; molecular weight 10,400 g mol−1) have been studied at both hydrophilic and hydrophobic surfaces. Their morphology at silica and mica surfaces was imaged with quantitative nanomechanical property mapping atomic force microscopy (QNM AFM), and friction and surface forces they mediate under confinement between two surfaces were studied using colloidal probe AFM (CP-AFM). We find that the polymersomes remained intact but adopted flattened conformation once adsorbed to mica, with a relatively low coverage. However, on silica these polymersomes were unstable, rupturing to form donut shaped residues or patchy bilayers. On a silica surface hydrophobized with a 19 nm polystyrene (PS) film, the polymer vesicles formed a more stable layer with a higher surface coverage as compared to the hydrophilic surface, and the interfacial structure also evolved over time. Moreover, friction was greatly reduced on hydrophobized silica surfaces in the presence of polymersomes, suggesting their potential as effective aqueous lubricants.</p

Staphylococcus aureus pathogenicity in cystic fibrosis patients-results from an observational prospective multicenter study concerning virulence genes, phylogeny, and gene plasticity

Staphylococcus aureus and cystic fibrosis (CF) are closely interlinked. To date, however, the impact of S. aureus culture in CF airways on lung function and disease progression has only been elucidated to a limited degree. This analysis aims to identify bacterial factors associated to clinical deterioration. Data were collected during an observational prospective multi-center study following 195 patients from 17 centers. The average follow-up time was 80 weeks. S. aureus isolates (n = 3180) were scanned for the presence of 25 virulence genes and agr-types using single and multiplex PCR. The presence of specific virulence genes was not associated to clinical deterioration. For the agr-types 1 and 4, however, a link to the subjects' clinical status became evident. Furthermore, a significant longitudinal decrease in the virulence gene quantity was observed. Analyses of the plasticity of the virulence genes revealed significantly increased plasticity rates in the presence of environmental stress. The results suggest that the phylogenetic background defines S. aureus pathogenicity rather than specific virulence genes. The longitudinal loss of virulence genes most likely reflects the adaptation process directed towards a persistent and colonizing rather than infecting lifestyle